The west coast main line fiasco was rooted in an irresponsible decision to rush into a complex programme of railway refranchising with a depleted staff, a cross-party group of MPs has reported.

The transport select committee found that civil service errors compounded this "recipe for failure", which eventually led to the award of Britain's most lucrative rail franchise to FirstGroup scrapped after Virgin's legal challenge.

While the report builds on the findings of Sam Laidlaw's inquiry that blamed civil servants for making mistakes and not escalating concerns to the heads of the department for transport, it concludes: "Embarking on an ambitious, perhaps unachievable, reform of franchising, in haste, on the UK's most complex piece of railway was irresponsible and involved such an element of risk that greater senior executive oversight and relevant technical expertise was required."

The committee said there were "lessons for ministers" and that the transport secretary, Patrick McLoughlin, should demonstrate he has learned them. But more direct and scathing criticism of ministers was vetoed from the final report by Conservative members, three of whom later also disassociated themselves from the word "irresponsible" and other conclusions.

Louise Ellman MP, chair of the committee, said: "This episode revealed substantial problems of governance, assurance, policy and resources inside the Department for Transport. Embarking on an ambitious – perhaps unachievable – reform of franchising, in haste, on the UK's most complex piece of railway was an irresponsible decision for which ministers were ultimately responsible.

"Many of the problems with the franchise competition, detailed in the Laidlaw report, reflect very badly on civil servants at the DfT. However, ministers approved a complex – perhaps unworkable – franchising policy at the same time as overseeing major cuts to the department's resources. This was a recipe for failure which the DfT must learn from urgently."

The committee called on McLoughlin to give further explanation of why ministers were misled over crucial errors and to conduct a search of DfT emails – promised in the first inquiry by Sam Laidlaw – to resolve questions of deliberate bias in the bidding process. The MPs also demanded a full account of costs of the debacle, which McLoughlin initially set at a direct £40m to compensate bidders.

The west coast process was scrapped in October after an internal review found "significant technical flaws" in the way the bid was run, and Virgin will now continue to run the London-Manchester-Glasgow line until late 2014. Three other franchise competitions are currently on hold.